What is the CVSS score of CVE-2026-65791?

CVE-2026-65791 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.6%.

Which versions of Windows iSCSI Target are affected by CVE-2026-65791?

Windows iSCSI Target Service contains a critical remote code execution vulnerability (CVSS 9.8) that allows unauthenticated network attackers to compromise storage infrastructure with no user…. A patch is available.

How to fix or mitigate CVE-2026-65791?

Within 24 hours: Audit all Windows iSCSI Target Service deployments and verify network exposure; immediately implement firewall rules to restrict iSCSI port 3260 to known authorized hosts only and disable the service if not actively in use. Within 7 days: Establish enhanced monitoring for iSCSI port 3260 connections to detect exploitation attempts, document all systems requiring iSCSI functionality, and create a prioritized remediation timeline. Within 30 days: Implement network segmentation to isolate iSCSI-dependent systems to dedicated VLANs, deploy intrusion detection signatures for iSCSI port 3260 traffic, and monitor vendor security advisories for patch availability to test and deploy immediately upon release.

Windows iSCSI Target CVE-2026-65791

EUVD-2026-56738 CRITICAL

Heap-based Buffer Overflow (CWE-122)

2026-08-11 secure@microsoft.com

GHSA-748w-4ph6-frjx

Buffer Overflow Heap Overflow Microsoft Windows 10 1607 Windows 10 1809 Windows Server 2012 Windows Server 2016 Windows Server 2019 Windows Server 2022 Windows Server 2025

9.8

CVSS 3.1 · Vendor: microsoft

Severity by source

Vendor (microsoft) PRIMARY

9.8 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

ENISA EUVD

HIGH

qualitative

vuln.today AI

9.8 CRITICAL

Network-facing iSCSI parser reachable pre-authentication with no user interaction (AV:N/AC:L/PR:N/UI:N); heap RCE in a SYSTEM-context service yields full C:H/I:H/A:H.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Patch available

Aug 11, 2026 - 18:19 EUVD

Analysis Generated

Aug 11, 2026 - 18:17 vuln.today

CVE Published

Aug 11, 2026 - 17:18 nvd

CRITICAL 9.8

DescriptionCVE.org

Heap-based buffer overflow in Windows iSCSI Target Service allows an unauthorized attacker to execute code over a network.

AnalysisAI

Remote code execution in the Windows iSCSI Target Service allows an unauthenticated network attacker to run arbitrary code by exploiting a heap-based buffer overflow (CWE-122) in the service's network-facing request handling. The flaw carries a critical 9.8 CVSS rating and is remotely reachable with no privileges or user interaction, meaning any exposed iSCSI Target endpoint can be compromised end-to-end. No public exploit identified at time of analysis, and the vulnerability is not listed in CISA KEV.

Technical ContextAI

The iSCSI (Internet Small Computer Systems Interface) Target Service is the Windows Server role that presents block storage over TCP/IP (typically TCP port 3260), letting initiators mount virtual disks across the network as if they were local SCSI devices. The vulnerability is a CWE-122 heap-based buffer overflow: attacker-controlled data parsed from an iSCSI Protocol Data Unit (PDU) is copied into an undersized heap allocation, corrupting adjacent heap metadata or objects. Because the parsing occurs before authentication in the network-facing target service, a corrupted heap can be leveraged to hijack control flow and execute code in the context of the service (typically SYSTEM-level on Windows Server). The single NVD/MSRC reference confirms this is a Microsoft-reported issue but provides no low-level technical detail beyond the CWE classification.

RemediationAI

Apply the Microsoft security update for CVE-2026-65791 as published in the MSRC Security Update Guide (https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-65791); the exact patched build numbers and KB identifiers are listed there per affected Windows Server version and were not included in this input, so consult the advisory for the precise fix. Until the patch is deployed, reduce exposure by restricting network access to the iSCSI service - block or firewall inbound TCP port 3260 so only trusted initiator hosts on the storage network can reach the target, and where the role is not required, remove the iSCSI Target Server feature entirely. The trade-off of these controls is that firewalling or removing the role will break legitimate iSCSI initiators that mount storage from the target, so validate storage dependencies before applying them. Patch status: patch availability and exact fix version should be confirmed from the vendor advisory (no exact fix version was provided in this input).